Crystallization of lactitol, crystalline lactitol product and use thereof

ABSTRACT

The present invention relates to a novel process for the crystallization of lactitol, to a particulate crystalline lactitol product having novel properties, to the use thereof as in foodstuffs, pharmaceuticals and oral hygiene products, as well as to special lactitol sweeteners. The process comprises: contacting a liquid containing dissolved lactitol with gas suspended fine solid particles containing microcrystalline lactitol; causing substantial removal of the solvent component of said liquid and allowing the resulting lactitol material to form an essentially solid composition of matter comprising a multitude of microcrystals of lactitol; and causing said lactitol composition to be conditioned during a further step to provide a product consisting essentially throughtout its entire structure of a multitude of microcrystals of lactitol agglomerated together in a random manner. The invention provides a crystalline lactitol product consisting essentially throughout its entire structure of a multitude of microcrystals of lactitol agglomerated together in a random manner.

The present invention relates to a novel process for the crystallizationof lactitol, to a particulate crystalline lactitol product having novelproperties, to the use thereof as in foodstuffs, pharmaceuticals andoral hygiene products, and to a special sweetener. The present inventionspecifically provides a crystalline lactitol product, wherein thecrystals are produced by microcrystallization of lactitol from a liquidsolution of lactitol.

Lactitol is a sweetener which can be used as a total or partialreplacement for sucrose, however, its energy content is only about halfof that of sucrose, and it does not cause increased blood glucosecontent; furthermore, it is non-cariogenic and hence tooth-friendly.Lactitol also can be used as an active ingredient and an excipient inpharmaceutical preparations, e.g. as a laxative.

The preparation of lactitol from lactose has been known for a long time.Industrially, lactitol is prepared from lactose by hydrogenation in thepresence of a Raney nickel catalyst. The preparation is described e.g.in Wolfrom, M. L., et al., J. Am. Chem. Soc. 60, (1938) p. 571-573.

Crystalline lactitol is reported to occur in the anhydrous form as wellas in the form of a monohydrate and dihydrate. Lactitol alsocrystallizes as a trihydrate. There seem to exist more than one distinctcrystalline form of anhydrous lactitol.

Crystalline lactitol monohydrate as well as the di- and trihydrate andanhydrous lactitol may be used as sweetening agents resembling sugar.For instance, crystalline lactitol monohydrate may be used in dieteticproducts, confectionery, bakery products, cereals, desserts, jams,beverages, chocolate, chewing gums and ice-cream. The lactitol crystalsmay also be used in the production of oral hygiene products such astooth pastes, and in the manufacture of pharmaceuticals.

Anhydrous lactitol may be crystallized from an aqueous solution asdescribed in WO 92/16542. incorporated herein by reference. Anhydrouslactitol has a melting range of 149-152° C.

Lactitol hydrate powders dehydrated to a moisture content of less than3% have been prepared by drying both lactitol solution and crystallinehydrate. The hygroscopicity of these powders is utilized in drying moistmixtures (European Patent Application 0231643).

Crystallization of lactitol from aqueous solutions and the crystalstructures of lactitol have been reported, among others, in vanVelthuijsen, J. A., J. Agric. Food Chem. 27, (1979) p. 680; EuropeanPatent 0 039 981; J. Kivikoski et al. Carbohydrate Research, 233 (1992)53-59; EP Patent Application 0 381 483; EP Patent 0456636; JP PatentApplication 13220/89. The disclosures of said publications areincorporated herein by reference.

The crystallization of lactitol from a liquid such as from an aqueous orethanolic solution requires specific crystallization conditions andfairly long crystallization times. Due to the nature of prior artsuspension crystallization methods, all of the lactitol in the solutiongenerally cannot be obtained in crystalline form. A part of the lactitolwill always remain in the mother liquor and will be discarded with themother liquor even after repeated series of crystallizations.

Lactitol can also be produced in solid form by granulation as describedin background art PCT/FI97/00548. Spray drying of lactitol has also beenattempted according to JP open-laid Patent Hei 2-255694 but the testsmade were accompanied by many problems. Co-spray drying of a polyolcomposition containing mainly mannitol and up to 10% lactitol isdescribed in WO 97/39739.

Thus, there exists a need for improving the production of solid lactitoland the present invention aims at satisfying that need.

The object of the present invention is thus, to provide a solidparticulate crystalline lactitol product.

Another object of the present invention is to provide crystallinelactiol in a process which transforms a lactitol liquid into a solidlactitol product in one single overall operation.

An object of the invention is also to provide a novel particulatelactitol product which is suitable for use in the food industry as wellas in the pharmaceutical and oral hygiene product industry.

A further object of the present invention is to provide a directlycompressible lactitol product.

An object is also to provide novel edible, pharmaceutical and oralhygiene products containing lactitol.

Consequently, the present invention, as defined in the appended claims,provides a novel process for producing crystalline lactitol. Saidprocess comprises contacting a liquid containing dissolved lactitol withgas suspended solid particles containing solid lactitol; causingsubstantial removal of the solvent component of said liquid and allowingthe resulting lactitol material to form a composition of mattercomprising a multitude of microcrystals of lactitol; and causing saidlactitol composition to be conditioned during a further drying step toprovide a product consisting essentially throughout its entire structureof a multitude of microcrystals of lactitol agglomerated together in arandom manner.

In a preferred embodiment of the invention an aqueous solution oflactitol is got into contact with fluidized particles ofmicrocrystalline lactitol, the wetted particles are dried in a flow ofwarm gas, and the lactitol on the surface of the particles is allowed toform new microcrystals.

By further conditioning the particles, the microcrystallization isallowed to proceed for a sufficient time to provide a final productconsisting essentially of microcrystalline lactitol.

In a preferred embodiment of the invention the wetted particles aresubstantially dried while falling down with a co-current air stream andallowed to settle into a porous layer of agglomerated microcrystallizinglactitol, which is then conditioned and cooled. The microcrystallizationconditions are selected so that the cooled layer is porous and brittle.If desired, the layer may be broken up into smaller fractions. Only amild crushing action is needed to break up the agglomerated mass ofmicrocrystals. The agglomerated product will primarily be broken up atthe interfaces between individual crystals rather than by disrupting thecrystals themselves.

In another embodiment of the invention the particles are retained in agas suspended state in an air stream while additional liquid is sprayedonto their surfaces until the particles have grown to a predeterminedsize or weight. The particles are then removed from the air stream, e.g.by gravity and conditioned as described above.

The gas suspended microcrystalline lactitol particles are preferablyprovided by recirculating a portion of the microcrystalline lactitolproduced in the process itself. Said particles may comprise dustentrained in circulating drying air or it may be dust or fine particlesprovided by the crushing of the agglomerated mass. At start-up milledcrystalline lactitol may be used as solid feed to be replaced bymicrocrystalline lactitol when available.

The terms “microcrystalline” and “rnicrocrystal” as used throughout thepresent specification and claims should be understood to mean very smallcrystals having a size which on an average is below 50μ, and generallyis of the order of about 5-10μ, on an average. In contrast to thepresent microcrystals, the lactitol crystals obtainable by prior knowncrystallization techniques are discrete crystals which, on an average,are of the order of about 100-1000μ or larger.

Consequently, the present invention provides a novel particulatecrystalline lactitol product wherein each particle substantiallythroughout its entire structure consists of a multitude of microcrystalsof lactitol agglomerated together in a random manner.

Although the size of the lactitol particles according to the presentinvention is not critical and may vary according to the intended use ofthe product, the mean particle size of the lactitol product is generallybelow 10 mm, typically between about 0.1 and 2.0 mm. The preferred meanparticle size is generally about 0.15-0.4 mm. The particle size anddistribution may be control-led to sure intended use.

The microcrystals may be used as said discrete particles, they may becompressed and tabletted or they may even be given the form of ordinarysugar lumps or cubes.

The individual lactitol microcrystals generally comprise anhydrouslactitol and/or lactitol monohydrate. The crystal mass may also includeother lactitol hydrate forms, such as lactitol dihydrate and/oramorphous lactitol. It is, however, for many applications preferred thatthe major crystalline form is anhydrous or monohydrate. In a preferredembodiment of the invention, the microcrystals consist essentially ofanhydrous lactitol.

The microcrystalline lactitol product according to the present inventionmay be used as a bulk sweetener for the total or partial replacement ofsucrose or other sweetening agents. Thus, it is useful in dieteticproducts, confectionery, bakery products, cereals, desserts, jams,beverages, chocolate, chewing gums and ice creams. It is also useful inpharmaceuticals such as laxatives and in oral hygiene products such astooth pastes.

The microcrystalline lactitol product according to the present inventionis particularly useful for tabletting purposes due to its agglomeratedcrystal structure, and partly also because of the presence of differentphysical forms of particles. The product may, for instance, be used as atabletting excipient in the same way as lactose.

A further embodiment of the present invention relates to a specialsweetener which comprises microcrystalline lactitol. Such a sweetenermay include other components such as excipients and/or other sweeteners.

Such other sweeteners are preferably also non-cariogenic sweeteners suchas intense sweeteners taken from the group comprising dipeptidesweeteners, saccharin, acesulfame K, stevioside, cyclamate, sucraloseand neohesperidin dihydrochalcone. However, the preferred non-cariogenicsweetener consists essentially of the microcrystalline lactitolaccording to the invention.

The excipients which may be used in the sweetener and/or otherapplications such as in pharmaceutical preparations may comprise, forinstance, microcrystalline cellulose, carboxymethyl cellulose,polydextrose, dextrose, maltodextrin, lactose, sugar, etc. as well asother sugar alcohols. The microcrystalline lactitol according to thepresent invention may also be used in preparations as a substantiallyinert component such as a diluent, carrier and/or excipient.

The microcrystalline lactitol of the present invention is preferablyproduced in a pure lactitol form, i.e. containing throughout essentiallyonly lactitol. Although the lactitol may be mixed with other compounds,lactitol should always form the major portion of the composition andpreferably the product should contain over 80%, preferably more than 90%and most preferably more than 98% lactitol.

If the solid and/or liquid feed comprises other components, such as oneor more of the above mentioned excipients, or other active ingredients,the product discharged from the microcrystallization apparatus willcontain said other component(s) as an integral part of its structure. Asecondary spray of another solid or liquid component may also be fedinto the microcrystallization apparatus into contact with themicrocrystallizing lactitol. Said other compounds should be selected soas to not interfere adversely with the microcrystallization of thelactitol.

Further embodiments of the present invention relate to products madefrom the novel microcrystalline lactitol. Such products are typicallyedible products, pharmaceutical products and/or oral hygiene productssuch as those mentioned above. Special advantages are obtained, forinstance, in the production of chocolate from the microcrystallinelactitol of the present invention.

A further embodiment of the invention relates to a directly compressiblecrystalline lactitol product comprising the novel microcrystallinelactitol and to tablets produced by compressing a composition containingsuch microcrystalline lactitol.

The present invention will now be described in greater detail. Thisdescription should, however, not be taken as limiting the invention tothe precise wording thereof. A person skilled in the art will be able toprovide numerous modifications and variations of the process withoutdeviating from the invention as defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The microcrystalline lactitol produced according to the presentinvention is shown in the accompanying drawing, wherein

FIG. 1 is a SEM photo showing the microcrystalline structure in 400×magnification.

FIG. 2 is a SEM photo showing the microcrystalline structure in 4800×magnification.

In the process according to the present invention a liquid containingdissolved lactitol is provided. The solvent component of said liquid ispreferably water, although lactitol may also be microcrystallized fromother solvents such as alcohols, e.g. isopropanol.

The lactitol concentration of said aqueous solution should be betweenabout 30% by weight and about 80% by weight in order to provide asuitable supersaturation at the crystallization. Said concentration ispreferably about 40-70% by weight.

Prior to feeding the liquid into a microcrystallization apparatus, theliquid is preferably warmed in order to facilitate the subsequentremoval of the solvent component and in order to more quickly providesuitable crystallization conditions in said apparatus. An aqueoussolution is preferably warmed to a temperature of about 45-80° C.preferably about 50-70° C. prior to feeding into said apparatus.

The liquid should preferably be distributed in the form of smalldroplets in the microcrystallization apparatus. The liquid is preferablyfed at a pressure through one or more nozzle(s) into said apparatus. Inthe apparatus liquid is brought into contact with solid particlescontaining solid lactitol which are simultaneously fed into theapparatus so as to be fluidized or suspended in said apparatus.

The solid lactitol particles may comprise microcrystalline lactitolparticles recirculated from the microcrystallization apparatus. Mostpreferably a fine fraction of the product is recirculated. Such a finefraction typically has a mean particle size below about 0.2 mm,preferably below about 0.1 mm. However, when larger individual productparticles are desired, correspondingly larger lactitol particles may berecirculated or fed into the apparatus from another source. The solidparticles may also be dust or fine particles entrained in the drying airand fed back into the apparatus as solid feed.

The liquid is generally contacted with the suspended solid particles inan upper portion of the microcrystallization apparatus. Here the wettedparticles and any free droplets of lactitol solution meet a drying gassuch as heated air which is introduced into the apparatus to provideremoval of the solvent component of said liquid. The drying air ispreferably heated to a temperature of about 60-200 ° C., preferablyabout 90-160° C., most preferably to about 100-130° C. A highertemperature favours the production of anhydrous lactitol, while a lowertemperature allows formation of lactitol monohydrate and/or otherhydrate forms.

The drying should be accomplished in such a way as to substantiallyremove the solvent while said lactitol material is still in a suspendedstate. When the solvent is water, said drying should provide a suspendedlactitol material dried to a free moisture content of about 0.1 to 5%,preferably 0.1 to 3%. The free moisture is calculated as any water whichis not bound as crystal water in the microcrystallizing lactitol.

In case the drying is not sufficient or too much liquid has been fedinto the apparatus, the lactitol material will be too wet and thecrystals will stick together to form a dense structure.

The suitable ratio of lactitol liquid to solid lactitol varies with themicrocrystallization conditions. The ratio should be selected so as toprovide a wetting of the solid particle surfaces without dissolving thecore of the seed particles. The amount of solvent component also dependson the ease of volatilization of the solvent and on the temperature ofthe liquid feed as well as the temperature and amount of the drying gas.

The wetted particles may be dried by a co-current or a counter-currentstream of drying air. The co-current air will flow downwards with thefalling particles while a counter-current air stream will retain theparticles in a suspended state for a longer time.

The particles carried downwards with a co-current air stream in amicrocrystallization apparatus should be substantially dry by the timethey reach the bottom portion of the apparatus and are allowed to settlethere. The settling surface is preferably a means allowing building upof a suitable layer and for adjusting the reaction time in the layer. Abelt moving at a speed sufficient to allow build up of a porousagglomerated layer of lactitol is generally sautable. The layertypically has a thickness of about 0.5 to 5 cm, preferably about 1-3 cm.

The agglomerated layer of solidified lactitol should further beconditioned so as to allow microcrystallization to proceed in the layer.Said conditioning preferably includes two or more separate steps orphases with different temperatures. The layer is heated e.g. by blowinga drying gas therethrough. The temperature and amount of the drying gasis selected so as to provide suitable microcrystallization conditions inthe layer. A higher temperature will favour the formation of anhydrouslactitol. The temperature of the drying gas is typically about 50-160°C. A conditioning at a temperature of about 50-70° C. will favourproduction of lactitol monohydrate microcrystals while a conditioningtemperature of about 80-130° C. will produce predominantly anhydrouslactitol microcrystals.

The conditioning should continue for a sufficient time to allowmicrocrystallization of any solubilized lactitol to take place in thelayer. Typically, the conditioning should continue for a time of about10-180 min or more, preferably about 20-40 min.

After conditioning, the agglomerated particle layer is preferablypost-conditioned and cooled or is allowed to cool to ambienttemperature. If the surface on which the layer is allowed to settle isflat, the result will be a substantially flat porous and brittle platecomprising microcrystalline lactitol. However, the microcrystallizinglactitol may also be gathered in forms or molds having any desired formsuch as resembling ordinary sugar lumps, or bars, strings, cubes,spades, hearts, flowers, etc.

When the microcrystalline product is in the form of a continuous layer,it is generally desirable to break up the agglomerated layer to providediscrete particles. Only a mild comminuting action is required forbreaking up the bonds between individual microcrystals.

The resulting microcrystalline lactitol particles are preferablyfractionated after an eventual milling and a portion thereof isrecirculated to provide a feed of solid particles containingmicrocrystalline lactitol into the top portion of themicrocrystallization apparatus.

Generally the microcrystalline lactitol particles are broken up so as toprovide particles having a mean particle size of about 0.1-10 mm,preferably about 0.15-0.4 mm. It is generally desirable to recirculatefine particles having a mean particle size below about 0.2 mm,preferably below about 0.1 mm, although larger particles may berecirculated, especially in cases where the desired end productcomprises larger particles.

In the case where the drying air is blown counter-current to thedownward movement of the wetted particles in the microcrystallizationapparatus, the particles will be fluidized therein. By a suitablefluidization action the particles will be made to recirculate within theapparatus. In the apparatus a simultaneous wetting, drying andmicrocrystallization of particles will take place. Each particle willpass through several wetting and drying/microcrystallization stages,colliding with other particles and growing ever bigger until theparticle reaches the size and weight wherein the fluidizing air nolonger manages to retain them in a fluidized state. At this stage theparticles will fall to the bottom of the apparatus and may be removedtherefrom to be conditioned, for instance as described above.

The solid feed to the microcrystallization apparatus in thecounter-current case preferably comprises dust, and fine particlesrecovered from the circulation of drying air.

In the particulate microcrystalline lactitol product according to thepresent invention each particle substantially throughout its entirestructure consists of a multitude of microcrystals of lactitolagglomerated together in a random manner. The lactitol purity of theproduct is preferably more than 80%, preferably more than 90%, mostpreferably up to 98% or more.

In the preferred particles about 10-90%, preferably about 30-70% of thedry substance derives from a feed of solid microcrystalline particles,preferably recirculated from the production line or from the drying air.The co-current system may require slightly more solid feed than does thecounter-current system. Thus, for the co-current driving system. thepreferred amount of dry substance deriving from the solid particles is50-70%.

The microcrystals in each product particle of the present invention areindividually very small compared to the crystals formed by prior artcrystallization processes. Generally, the size of the microcrystals ineach particle is on an average below 50μ, preferably about 5-10μ on anaverage.

Depending on the production parameters, especially the temperature usedduring microcrystallization, the lactitol crystallizes predominantlyeither as monohydrate or anhydrous microcrystals. Higher temperaturesfavour the production of anhydrous crystals. The particles may comprisepure individual crystalline forms, or they may comprise mixtures ofvarious forms of lactitol crystals. Lactitol hydrate forms containingtwo or three molecules of bound crystal water may also form initiallybut the drying conditions are generally selected so as to make thesehydrates lose at least some of the bound water. A mixture of lactitolmonohydrate and anhydrous lactitol crystals with some amorphous lactitolis generally produced.

The degree of crystallinity of the product is, however, generally high.According to DSC measurements the degree of crystallinity is generallyas high as 90% or more.

The water content of the preferred microcrystalline lactitol productvaries according to production parameters in the range of 0.1% to about6%. Thus, the microcrystalline lactitol product according to theinvention quite often will have a water content between those of pureanhydrous lactitol and pure lactitol monohydrate.

The melting behaviour generally shows peaks, measured with differentialscanning calorimetry (DSC), at least at the melting ranges of lactitolmonohydrate (about 95-100° C.) and anhydrous lactitol (about 145-150°C.). However, there are frequently DSC peaks also at the melting rangeof another anhydrous form (about 120-123° C.) and even at the dihydratemelting range (about 72-78° C.). The actual melting usually takes placeat the higher anhydrous lactitol melting range since there is almostalways some anhydrous lactitol in the sample. Since the particlescontain a myriad of small crystals with mutually different meltingbehaviours, the product generally cannot be regarded as a purecrystalline form of lactitol.

The invention will now be illustrated with the aid of a few examples.These examples should in no way be taken as limiting the invention.

EXAMPLE 1

A lactitol solution (concentration 49.6% by weight, purity over 99% onD.S.) was fed into a heated feed tank. The temperature of the solutionin the feed tank was kept at 52±2° C. Solution was supplied from thetank to a top spray nozzle at a rate of 28 kg/h. The feed pressure ofthe solution varied from 130 to 150 bar.

Simultaneously with the solution small particles of dried product werefed to the nozzle at a rate of 23 kg/h. Drying air was also fed into theapparatus to dry the sprayed solution and wetted particles. Thetemperature of the air was adjusted to about 100-105° C. The partlydried droplets and dry feed mixture fell co-currently with theair-stream towards the bottom screen having a temperature of 45-65° C.

The apparatus was operated under these conditions for nine minutes.During this time an agglomerated, porous powder layer having a thicknessof about 2 cm built up on the screen. The lactitol layer was conditionedon the screen for about 30 minutes and the temperature dropped slowlyfrom 50° C. to 45° C. The microcrystallized product was collected fromthe screen, subjected to a gentle milling and sieved.

The water content of the microcrystalline lactitol product was found tobe 3.5%.

EXAMPLE 2

The procedure of Example 1 was repeated several times under varying testconditions. The solid feed comprised recirculated microcrystallinelactitol. The test conditions are indicated in Table 1.

The water content of the microcrystalline lactitol product was analyzedby the Karl Fischer method and the melting behaviour was measured bydifferential scanning calorimetry (DSC).

The analysis results of the products are shown in Table 2.

TABLE 1 Lactitol microcrystallization conditions Feed Time pressure Feedsoln. temp. Drying air Temp. under Temp. above Feed End DS fr. Test minbar Conc. D.S. % ° C. temp. ° C. screen ° C. screen ° C. dry kg prod. kgsoln. % 1 0 30 51.1 50-54 100 64 64 2.5 15 40 112 54 52 7.0 64 2 0 6051.1 50-54 108 65 64 3.3 6 45 119 58 58 4.1 20 3 0 30 51.1 50-54 104 7072 2.8 6 50 108 57 57 4.0 30 4 0 75 49.6 50-54 100 71 69 4 16 80 100 5050 6.6 39 5 0 40 49.6 50-54 96 58 61 3 19 70 109 52 55 5.5 45 6 3 9049.6 50-54 99 53 55 3 8 110 102 45 48 4.3 30 7 0 80 49.6 50-54 96 58 611.9 4 80 104 49 50 2.8 32 8 0 100 49.6 50-54 126 74 82 3.6 9 130 98 4547 5.9 39 9 0 140 49.6 50-54 100 57 65 3.5 9 130 104 44 47 5.6 38 10 050 54.2 64-67 81 57 57 4.4 8 60 100 48 52 5.6 22 11 0 70 54.2 64-67 8059 57 4.9 10 110 99 52 54 8.4 42

TABLE 2 Water contents of the product Water DSC peaks at Test %Description ° C. ° C. ° C. 1 4,5 Good layer 86,4 150,6 2 0,6 Good layer96,1 122 152,5 3 2,6 Good layer 93,8 152,3 4 3,9 Good layer 94,5 152 55,3 Good layer 93,9 142,9 6 3,8 Good layer 94,3 152,5 7 2,4 Good layer76,8  92,4 152,9 8 5,1 Good layer 93,9 146,5 9 3,5 Good layer 78,4  93,3153,4 10 5,0 Good layer 96,7 134,1 145,3 11 5,4 Good layer 97 146,8

The degree of crystallinity was measured for runs No. 10 and 11 by DSCand was found to be 94 to 95%.

EXAMPLE 3

A continuous fluid bed microcrystallization is performed in an apparatushaving a fluid bed drying chamber, equipped with a spray nozzle systeminside in the middle of the chamber. The apparatus comprises a bottomscreen with a hole for the discharge of the heaviest particles, and acyclone to recover light particles.

The chamber is loaded with 1 kg of powdered lactitol to act as seedmaterial for the microcrystallization of lactitol. The powdered lactitolis fluidized with a flow of air (temperature 100-105° C.) through thebottom screen. A lactitol solution (concentration 50%, purity over 99%D.S.) at a temperature of 50° C. is fed into the chamber with a pump,atomized by means of a nozzle and sprayed over the fluidized lactitolpowder.

The solution is supplied at a rate of 1 kg/h to the fluidized lactitolpowder. The air flow rate is adjusted to fluidize the lactitol and toevaporate water at a rate sufficient to crystallizes the lactitol. Amicrocrystalline lactitol agglomerate is formed when lactitolcrystallizes around the lactitol powder particles. The agglomeratesremain in a fluidized state until they fall down when their weight ishigh enough. Lactitol agglomerates are discharged continuously throughthe bottom hole.

In the drying chamber the lightest, non-agglomerated lactitol particlesare removed from the top of the chamber entrained in the exiting airstream. This fine lactitol material is recovered in a cyclone and fedback to the chamber to act as a continuous seed stream.

The discharged agglomerated product is conditioned at a temperature of45-50° C. for 30 minutes to balance the microcrystallization.

Steady state conditions are reached when all the powdered lactitol usedas a starting seed has been discharged from the process. The productobtained thereafter is a totally microcrystalline product whichthroughout its entire structure consists of microcrystalline lactitol.

EXAMPLE 4

A microcrystalline lactitol product having a water content of about 5%was assessed in a standard chocolate production.

The following ingredients were used

Cocoa Liquor (BCM) 13.4% Full Cream Milk Powder (Kerrygold Ingredients)13.4% Microcrystalline lactitol 44.0% Litesse II (Cultor Food ScienceInc.)  4.8% Cocoa Butter (BCM) 23.7% Vanillin (Claremont Ingredients) 0.2% Lecithin  0.5%

The milk powder, microcrystalline lactitol, Litesse II (modifiedpolydextrose), vanillin and cocoa liquor were mixed in a Stephan mixerwith a portion of the cocoa butter. The mixture was passed through athree roll refiner to produce a flake. The flake was mixed again in theStephan mixer and a farther portion of cocoa butter was added. The mixwas re-refined with the pressures increased to produce a flake with anacceptable particle size.

The resulting flakes were stored ready for conching. Prior to conchingthe flakes were pre-warmed in an oven set to 50° C. The flake was addedto a conche with the temperature set to 60° C. On loading the remainingcocoa butter was added to give a final fat content of 35 %. A smallamount of the lecithin was added at this stage. The sample was conchedfor 24 hours. The remaining lecithin was added I hour prior to theremoval of the batch from the conche.

For the sake of comparison the procedure was repeated identically withanother batch except that the microcrystalline lactitol was replaced bystandard crystalline lactitol monohydrate (Lactitol MC, Xyrofin Oy).

During the production of the two batches there were no significantprocessing differences. Neither batch showed any difficulties and theresulting chocolates were both acceptable.

A particle size analysis of the two batches showed that an acceptableparticle size was achieved in both cases. There was an insignificantincrease in the particle size of the chocolate made usingmicrocrystalline lactitol (10-12 μm) compared to the one with lactitolmonohydrate (9-10 μm).

The viscosity of the two samples was measured using a Haake RV20viscometer with an RC20 rheocontroller fitted. It was found that theviscosity of the sample made with the microcrystalline lactitolaccording to the present invention showed no significant increase inviscosity when held at 50° C. for one week, while the sample withlactitol monohydrate showed considerable thickening when stored at 50°C. The absence of thickening in the chocolate made with themicrocrystalline lactitol is a distinct advantage over lactitolmonohydrate and completely unexpected for a sweetener containing about5% moisture, either free or bound.

EXAMPLE 5

A set of standard recipe madeira cakes were produced usingmicrocrystalline lactitol according to the present invention, commercialcrystalline lactitol (Xyrofin Oy) and milled lactitol (Xyrofin Oy).

The lactitols were respectively mixed with sorbitol, flour, high ratiofat, skimmed milk powder, egg, salt, baking, powder, spray dried eggpowder and acesulfame K. The mix was deposited in paper cases and cookedin the oven at 210° C. for 30-35 minutes.

The cakes produced with the microcrystalline lactitol were equally goodin quality as the two other batches.

EXAMPLE 6

A sample of microcrystalline lactitol produced according to the presentinvention was assessed in tablet production and compared to standardlactitol monohydrate (Lactitol MC, Xyrofin Oy) and a granulated lactitolproduct produced according to the teaching of the above mentioned PatentApplication PCT/FI97/00548 (Finlac DC, Xyrofin).

The material under evaluation was mixed in a laboratory scale Turbulamixer for 2 minutes with 0.5% magnesium stearate as lubricant. The mixedsample was then tabletted on a Manesty 2C single punch press using a 15mm diameter flat-faced bevelled edge punch.

The compression force was adjusted by altering the drop of the toppunch. The compression force is indicated by an arbitrary figure. Thehigher the number, the greater the compression. These figures can onlybe used as a comparison for each series of compressions. As soon as thematerial is changed or any of the machine settings are altered thenumbers cannot be compared. The adjustment is such that it cannot beexactly reproduced, therefore, these figures should only be seen as ameans of differentiating between samples and indicating eitherincreasing or decreasing compression force.

Tablet hardness was measured using a Key Instruments tablet hardnesstester which measures the force required to break the tablet across itsdiameter. Ten tablets were tested and an average reading recorded.

The thickness of ten tablets was measured using a micrometer gauge. Theaverage of ten tablets is recorded.

Ten tablets were weighed individually and an average recorded.

Tablet friability was measured using a Key Instruments friabilitytester. Ten tablets were dropped 100 times and the percentage weightloss recorded. Any tablets that are badly chipped are removed prior toweighing.

The results obtained from tabletting microcrystalline lactitol aretabulated in Table 3. This material tabletted well producing acceptabletablets over a range of compression forces. The maximum hardnessachieved was over 300 N. The friability of these tablets was acceptablefor all the tablets produced with hardness result >100N.

The results obtained from tabletting crystalline lactitol monohydrateare tabulated in Table 4. This material did not tablet well producingpoor compacts with a maximum hardness of <70N. In all cases the tabletswere poorly formed giving unacceptable friability results, with all ofthe tablets totally disintegrating during the test.

The results obtained from tabletting granulated lactitol are tabulatedin Table 5. This material produced good tablets over a range ofcompression forces. Hardness results obtained for these samples were notas high as those seen for the microcrystalline lactitol samples, with amaximum of 240N compared to >300N. The friability of the tabletsproduced with microcrystalline lactitol was still better than that ofthe tablets produced with granulated lactitol.

TABLE 3 Microcrystalline Lactitol Sample Compression* 34.5 34 33.5 3332.5 32 Weight (g) 0.981 0.994 0.979 0.981 0.995 0.998 Thickness 3.8593.9 3.864 3.95 4.18 4.4 (mm) Hardness (N) 330 134 319 252(257) 156(137)90(85) (344) (335) (301) Friability 0.69 0.38 0.5 0.22 0.32 1.31 (10tabs)

TABLE 4 Crystalline Lactitol Monohydrate Compression* 32.5 32 31.5 31Weight (g) 1.003 1.006 1.006 0.999 Thickness 4.019 4.055 4.046 4.52 (mm)Hardness (N) 61(59) 62(61) 67(64) 68(64) Friability 100 100 100 100 (10tabs)

TABLE 5 Granulated Lactitol Compression* 34 33.5 33 32.5 Weight (g)1.007 0.989 1.018 0.99 Thickness 4.029 4.138 4.414 4.614 (mm) Hardness(N) 240(307) 193(213) 139(133) 70(82) Friability 0.34 1.08 1.79 4.7 (10tabs)

Figures shown in brackets in Tables 3, 4 and 5 are those taken fromanalysis performed during production. All other results are fromanalysis performed ⁻24 hours after production.

While the standard crystalline lactitol monohydrate produced poortablets, the microcrystalline lactitol sample according to the presentinvention showed an improvement even when compared to the granulatedlactitol. Tablets that were produced had a higher hardness and producedacceptable tablets over a greater range of compression forces. Thefriability of these samples was also an improvement on the results seenfor the granulated lactitol sample.

EXAMPLE 7

A batch of microcrystalline lactitol produced in accordance with theprocedure described in Example 1 was analyzed as to its physicalproperties. The following analysis methods were used:

Moisture was measured using coulometric Karl Fischer titration

DSC analysis was made at a speed of 10° C./minute

Flowability: A 500 g sample was poured to a 500 ml measuring cylinder.The sample was tapped 10 times, levelled and the amount of the samplewas weighed.

Hygroscopicity: 10 g of the sample was weighed to a petri dish. The opendish was put into a humidity cabinet. The change in weight was measured.The humidity cabins at 25° C. and relative humidity 60% and at 40° C.and relative humidity 70% were used.

Particle size distribution: Sieve analysis was used to determine theparticle size.

Rate of solution: 100 g of the sample was put in 100 g of water at 20°C. and 40° C. A small paddle mixer, 250 rpm, was used to mix thesolution. During the dissolution the refractive index was measured.

Heat of solution: 40 g of the sample was dissolved in 670 g of distilledwater at 25° C. The heat of solution was measured with a calorimeteroperating in a constant temperature environment.

SEM photos were taken of the microcrystalline lactitol.

The microcrystalline lactitol was compared to a commercial gradelactitol monohydrate (Lactitol MC L125 lot 22117, Xyrofin Oy, Kotka,Finland). The analysis results are indicated in Table 3

TABLE 3 Analysis Microcryst. Monohydr. Moisture, % 5.1 5.1 DSC, 10°C./min, peak at 96.5 104.1 147.4 Flowability, s 17 23 Bulk density,g/500 ml 325 360 Heat of solution, cal/g 15.4 15.6 Sieve analysis >0.710mm 0.6 15.2 >0.560 mm 2.3 17.9 >0.450 mm 8.3 20.6 >0.315 mm 31.525.8 >0.250 mm 21.6 15.1 >0.180 mm 21.1 4.8 >0.100 mm 13.0 0.7 0 1.6 0.0Mean particle size, mm 0.29 0.47 Coefficient of variation 39 30

Both lactitols contained 5.1% of water. The DSC diagram of themicrocrystalline lactitol contained two peaks, while the monohydrate hadonly one. The microcrystalline lactitol had a better flowability and thebulk density was low. The mean particle size was lower for themicrocrystalline lactitol.

100 g of microcrystalline lactitol dissolved in 4 minutes. in 100 g ofwater at 20° C. compared to about 5 minutes for the monohydrate. Thesmaller particle size of the microcrystalline lactitol may be one reasonfor the quicker dissolution rate.

Microcrystalline lactitol absorbed water similarly to lactitolmonohydrate in both climate cabins. At 25° C. and 60% relative humiditythe water sorption of microcrystalline lactitol was 0.05% compared to0.02% for the monohydrate. At 40° C. and 70% relative humidity thefigures were 0.11% and 0.04%, respectively.

The microcrystalline lactitol in SEM photos in 400× magnification(FIG. 1) looked like crystal size lumps which contain small crystals.The microcrystalline structure shows very clearly in 4800× magnification(FIG. 2).

What is claimed is:
 1. A process for the crystallization of lactitol,comprising contacting a liquid containing dissolved lactitol withgas—suspended fine solid particles containing microcrystalline lactitol;causing substantial removal of the solvent component of said liquid andallowing the resulting lactitol material to form an essentially solidcomposition of matter comprising a multitude of microcrystals oflactitol; and conditioning said lactitol composition to provide aproduct comprising a multitude of microcrystals of lactitol agglomeratedtogether in a random manner.
 2. The process according to claim 1,wherein said liquid is an aqueous solution of lactitol having a lactitolconcentration of about 30-80% by weight.
 3. The process according toclaim 2, wherein said liquid is an aqueous solution of lactitol having alactitol concentration of about 40-70% by weight.
 4. The processaccording to claim 1, comprising warming said liquid to a temperature ofabout 45-80° C. prior to said contacting.
 5. The process according toclaim 4, comprising warming said liquid to a temperature of about 50-70°C. prior to said contacting.
 6. The process according to claim 1,wherein said contacting comprises spraying said liquid into contact withsaid suspended fine solid particles.
 7. The process according to claim1, wherein said liquid contains a minor portion of an excipient, anactive ingredient or other sweetener than lactitol.
 8. The processaccording to claim 7, wherein a secondary spray of another liquidcontaining an excipient, an active ingredient or other sweetener thanlactitol is simultaneously provided.
 9. The process according to claim1, wherein said removal of said solvent is performed by the introductionof a drying gas such as air heated to a temperature of about 60-200° C.10. The process according to claim 9, wherein said solvent is water andsaid solvent removal provides a lactitol material dried to a freemoisture content of about 0.1 to 5%, while said lactitol material isstill in a suspended state.
 11. The process according to claim 10,wherein said solvent and said solvent removal provides a lactitolmaterial dried to a free moisture content of about 0.1-3%, while saidlactitol is still in a suspended state.
 12. The process according toclaim 9, wherein said removal of said solvent is performed by theintroduction of a drying gas such as air heated to a temperature ofabout 90-160° C.
 13. The process according to claim 1, wherein saidconditioning comprises drying said lactitol composition.
 14. The processaccording claim 1, wherein said conditioning is maintained to allowlactitol microcrystallization to proceed in said composition.
 15. Theprocess according to claim 1, wherein said lactitol composition isallowed to settle on a moving belt and to form thereon a substantiallycontinuous agglomerated porous powder layer having a thickness of about0.5-5 cm.
 16. The process according to claim 15, wherein saidconditioning includes treating said composition in said agglomeratedlayer with a drying gas having a temperature of about 50-70° C., for atime of about 10-180 min or more, to provide a product comprising amajor portion of lactitol monohydrate.
 17. The process according toclaim 16, which further comprises cooling said conditioned agglomeratedlayer to provide a substantially flat porous and brittle platecomprising microcrystalline lactitol.
 18. The process according to claim17, comprising subjecting said plate to a mild comminuting action so asto break up said agglomerated layer.
 19. The process according to claim15, wherein said conditioning includes treating said composition in saidagglomerated layer with a drying gas having a temperature of about70-100° C. or more for a time of about 10-180 min or more to provide aproduct comprising a major portion of anhydrous lactitol.
 20. Theprocess according to claim 15, wherein said lactitol composition isallowed to settle on a moving belt and to form thereon a substantiallycontinuous agglomerated porous powder layer having a thickness of about1-3 cm.
 21. The process according claim 1, which further comprisesfractionating microcrystalline lactitol particles and recirculating atleast a portion thereof to provide a feed of said fine solid particlescontaining microcrystalline lactitol.
 22. The process according to claim21, comprising recovering microcrystalline lactitol particles having amean particle size of about 0.1-2 mm.
 23. The process according to claim22, comprising recovering microcrystalline lactitol particles having amean particle size of about 0.15-0.4 mm.
 24. The process according toclaim 1, wherein about 10-90% of the dry substance derives from a feedof solid microcrystalline particles.
 25. The process according to claim24, wherein about 30-70% of the dried substance derives from a feed ofsolid microcrystalline particles.
 26. The process according to claim 1,comprising recirculating microcrystalline lactitol particles having amean particle size below about 0.2 mm.
 27. The process according toclaim 26, comprising recirculating microcrystalline lactitol particleshaving a mean particle size below about 0.1 mm.
 28. The lactitol productaccording to claim 27, having a lactitol purity of more than 98%.
 29. Aparticulate crystalline lactitol product wherein each particlesubstantially throughout its entire structure consists of a multitude ofmicrocrystals of lactitol agglomerated together in a random manner. 30.The lactitol product according to claim 29, having a lactitol purity ofmore than 80%.
 31. The lactitol process according to claim 30, having alactitol purity of more than 90%.
 32. The lactitol product according toclaim 29, said particles having been produced by microcrystallization ofa liquid containing dissolved lactitol together with fine solidparticles containing microcrystalline lactitol.
 33. The lactitol productaccording to claim 29, wherein about 10-90% of the dry substance of thefinal product derives from a feed of solid microcrystalline particles.34. The lactitol product according to claim 29, comprising particleshaving a mean particle size of about 0.1-2.0 mm.
 35. The lactitolproduct according to claim 34, comprising particles having a meanparticle size of about 0.15-0.4 mm.
 36. The lactitol product accordingto claim 33, wherein about 30-70% of the dried substance of the finalproduct derives from a feed of solid microcrystalline particles.
 37. Thelactitol product according to claim 29, wherein the size of themicrocrystals in each particle is on an average below 50μ.
 38. Thelactitol product according to claim 37, wherein the size of themicrocrystals in each particle is about 5-10 μm.
 39. The lactitolproduct according claim 29, comprising a porous and brittle compositioncontaining microcrystals of anhydrous lactitol and lactitol monohydrate.40. The lactitol product according claim 29, wherein said microcrystalssubstantially comprise lactitol monohydrate.
 41. The lactitol productaccording to claim 29, wherein said microcrystals substantially compriseanhydrous lactitol.
 42. The lactitol product according to claim 29,wherein the microcrystals consist essentially of anhydrous lactitol. 43.The lactitol product according to claim 29, wherein said particulateproduct additionally contains components such as excipients, activeingredients or other sweeteners.
 44. A special sweetener which comprisesmicrocrystalline lactitol according claim
 29. 45. The special sweeteneraccording to claim 44 which is mainly composed of said microcrystallinelactitol.
 46. A bulk sweetener which comprises microcrystalline lactitolaccording to claim
 29. 47. A diluent, carrier or excipient comprisingmicrocrystalline lactitol according to claim
 29. 48. A tablet producedby directly compressing a composition containing microcrystallinelactitol produced by contacting gas-suspended microcrystalline lactitolparticles with a lactitol solution, drying said composition to causelactitol microcrystallization, and conditioning said composition toprovide a product comprising a multitude of microcrystals of lactitolagglomerated together in a random manner.
 49. An edible, pharmaceuticalor oral hygiene product which contains crystalline lactitol,characterized in that said product is selected from the confectionery,bakery products, cereals, desserts, jams, beverages, chocolate, chewinggum, ice cream, and dietetic products as well as in pharmaceuticalproducts such as laxatives or oral hygiene products such as tooth pasteand said lactitol is microcrystalline lactitol products by contactinggas-suspended microcrystalline lactitol particles with a lactitolsolution, drying the resulting composition to cause lactitolmicrocrystallization, and conditioning said composition to provide aproduct comprising a multitude of microcrystals of lactitol agglomeratedtogether in a random manner.
 50. A directly compressible crystallinelactitol product for tabletting, characterized in that said lactitolproduct is produced by contacting gas-suspended microcrystallinelactitol particles with a lactitol solution, drying the resultingcomposition to cause lactitol microcrystallization, and conditioningsaid composition to provide a product comprising a multitude ofmicrocrystals of lactitol agglomerated together in a random manner.